First pitch: Walker, one of the top prospects in baseball, debuts against Astros

Mariners righthander Taijuan Walker, who is rated as high as the fifth best prospect in baseball, is set to make his highly anticipated major league debut tonight at Minute Maid Park against the Astros.

Walker, 21, was a combined 9-10 between Class AA Jackson (4-7, 2.46 ERA) and Class AAA Tacoma (5-3, 3.61 ERA) this season, but he was 2-0 with an 0.82 ERA over his last two starts before earning a call to the majors.

In those games against Colorado and Tucson he scattered a combined nine hits and six walks with 15 strikeouts while giving up only one run through 11 innings, earning the most recent Pacific Coast League Pitcher of the Week award.

“He’s their top prospect for a reason,” Astros manager Bo Porter said. “Obviously it’s electric stuff. He’s had great success in the minor leagues. Our guys will be up for the challenge.”

Since being taken with the 43rd overall pick in the draft, he is 23-26 with a 3.49 ERA in his minor-league career over four seasons.

“Last year I had a lot of struggles,” he said. “I felt like I went back there with a purpose and with a goal in mind. I’ve been working really hard every day trying to get here. So finally all the hard work I put in is paying off.”

Walker expects to have nearly 30 friends and family members in town for his major league debut.

“I know I’m going to have some nerves in the first inning,” he said. “So hopefully I can just get it out of the way as fast as a I can and just get back to my normal self and pitch.”